Properties of wet granular materials with respect to screening process

The paper is the next one in a series presented at the last conference on this subject. It refers to screening of humid and wet materials and to the behaviour of these materials during mechanical processing. In the broad spectrum of environmental problems we often encounter processing of granular beds which in majority of cases consist of humid material containing such an amount of water which has a significant effect on mechanical processes as compared to the same process involving, however, dry material. It was proposed that the important parameter considered in the process was not material moisture content but the value of internal or external friction coefficient, as it appeared to be the one which determined the process and the difference between wet and dry process. So instead of determining empirically moisture content in the granular material, which is destined for the mechanical processing, it is necessary to determine experimentally values of friction coefficients (internal and external) and use them in further studies. The last element of the study is determination of the outflow function for screening of wet granular materials, being very important for screening of these materials. It constitutes a basis for new methods of screen designing, Furthermore so called transitional coefficient was introduced, which tells us about transition from dry screening to wet screening. Wet screening means such process in which presence of water in the material is important (can not be omitted).